The ever-increasing need for high quality mineral crystals, particularly as the building blocks for electronic components, has resulted in substantial progress in the development of techniques for growing synthethic crystals. One of the most successful techniques is the Czochralski or pulling methods. The pulling method is useful for growing crystals from the melt, when the crystal melts congruently, when the melt is of a low volatility, and when vessels which are non-reactive with the melt are available. The pulling method involves contacting a seed crystal with the surface of a nutrient melt and drawing the seed crystal away from the melt as the crystal grows at the interface. One drawback however, is that the resulting crystal is normally circular in cross-section. Because a circular cross-section is not the most economic from a processing point of view, it is desirable to somehow change this charcteristic of the system. One approach might be to isolate a certain area of the surface of the melt using a solid mask. The problem with a mask is that it would be very difficult to keep it from deteriorating due to the high temperature and reactivity of the nutrient melt for the period of time necessary to grow the crystals. This deterioration problem results in two unfavorable effects: first, the cross-sectional shape of the mask will change with time and thus cause an inconsistent crystal product and, second, the deteriorating mask will add impurities to the melt whose composition must be controlled within critical limits. These and other difficulties experienced with the prior art devices have been obviated in a novel manner by the present invention.
It is, therefore, an outstanding object of the invention to provide a system for growing crystals of a desired cross-section and, more specifically, crystals in sheet form.
Another object of this invention is the provision of a masking technique for use in the crystal pulling method.
A further object of the present invention is the provision of a masking technique for use in high temperature melts which does not contaminate the melt.
It is another object of the instant invention to provide a simple and relatively inexpensive method for providing electronic quality crystals of a shape which is optimum for subsequent processing.
With these and other objects in view, as will be apparent to those skilled in the art, the invention resides in the combination of parts set forth in the specification and covered by the claims appended hereto.